| 摘要 |
PURPOSE:To prevent the malfunction of the control circuit by detecting the AC signals of different frequencies given and then giving the control to other circuit with the detection output. CONSTITUTION:The detector of the control signal for the multiple voice broadcasting is supplied to terminal 10 in the TV picture receiver. The AC control signals for the stereo and multiple voice broadcasting each are applied to DC signal generator circuits 40 and 50 through filters 20 and 30. At the stereo broadcasting time, the output of circuit 40 drives transistor TrQ61 of detection circuit 60, and then the detection signal of stereo broadcast reception switching is obtained from terminal 80 and via TrQ71 and Q72. At the same time, TrQ1 is made to conduct along with light emitting diode L1 lit up to give the lamp display indicating the stereo broadcasting on the air. In this instant, the collector of TrQ1 features nearly the earth potential. With this earth potential, the base potential is clamped via diode D3 for voice multiple broadcasting control DC signal amplifier TrQ63. As a result, the malfunction caused by the noise or the like can be prevented for the multiple voice broadcasting. At the multiple voice broadcasting time, the malfunction is prevented for the stereo broadcasting in the same way. |
